1. Field of the Invention
The present invention relates to a device for transferring heat energy from a refrigeration circuit to a hot water system. More particularly, the present invention concerns a combination refrigerant desuperheater hot water heater, and a method of controlling same.
2. Description of the Prior Art
In the typical vapor compression refrigeration system various components such as a compressor, condenser, evaporator and expansion device are arranged to transfer heat energy between the fluid in heat exchange relation with the evaporator and fluid in heat exchange relation with the condenser. It is also known in conjunction with such refrigeration systems to utilize a desuper-heater for removing superheat energy from gaseous refrigerant prior to circulating said refrigerant to the condenser.
In a conventional building installation a hot water heater is provided to supply heated water to an enclosure.
Many hot water heaters have a cold water inlet connected to an inlet extension pipe and a hot water outlet extending through the top of the hot water tank. Often an inlet extension pipe is connected to the cold water inlet such that the incoming water is directed to the bottom portion of the tank. In hot water tanks water is heated at the bottom of the tank and rises such that a stratified tank with relatively warm water at the top and cool water at the bottom is provided. When demand is made for hot water, water is discharged from the top of the tank at its warmest temperature and cold water is supplied through the inlet to the bottom portion of the tank.
It is known to combine a refrigeration system and hot water heating system such that the superheat of the refrigerant may be rejected to water to be heated such that this heat energy may be utilized to provide hot water.
In air conditioning systems when cooling is required heat energy is transferred from the enclosure and discharged to the ambient or some other heat sink. This heat is often wasted. With the combination system as disclosed herein it can be seen that this heat energy that is unwanted in the enclosure may be utilized to supply heat energy to water to provide heated water for various end uses. This heated water may be used for bathing, cleaning, cooking or other uses in a residence. Commercial applications include restaurants, supermarkets, process utilization and any other application wherein waste energy or excess energy from a refrigeration system may be utilized to provide some or all of the hot water heating needs.
In addition to refrigeration systems providing excess heat for heating water during the cooling season, certain refrigeration circuits are capable of reversing the cycle of operation for providing heat energy to the enclosure during the heating season. If it is desirable some of the heat provided during the heating season may also be utilized to supply hot water through the disclosed hot water heater refrigerant desuperheater.
In the specific embodiment disclosed a pump is used to circulate water from the hot water tank through the heat exchanger and back to the hot water tank when the compressor of the refrigeration circuit is energized. A temperature sensing device is located to sense the temperature of the incoming water. A second temperature sensing device is located to sense the temperature of the water being discharged from the heat exchanger. When both of these devices sense the proper condition a solenoid valve is opened such that the pump circulates water through the heat exchanger and back to the hot water tank. Should either of these switches be closed the pump will continue to operate, however, water will then flow through a by-pass line located in parallel with the heat exchanger. This by-pass line has as a part thereof a flow restriction which substantially reduces the volume flow of water through the by-pass line as compared to the flow through the heat exchanger when the valve is in the open position. The combination of the pump operating continuously with the compressor and this flow restricted bypass line acts to provide for continual sensing of the water temperature in the tank and additionally serves to reduce the overall energy input to the pump and the wear on the pump caused by continual cycling. In addition thereto by allowing for the limited flow through the by-pass line the heat energy generated by the pump, albeit a small value, may be supplied to a relatively small flow of water.
Prior art devices disclose operating a pump continuously with a compressor, the use of a solenoid valve or other valve to control the flow of water through the heat exchanger and the use of a by-pass line to circulate the flow of water around the heat exchanger. None of these patents disclose the combination of operating the pump simultaneously with benefits achieved by utilizing a restricted by-pass.
Also there is disclosed a coaxial fitting for supplying heated water from the heat exchanger to the hot water tank. It has been found that the temperature of the water flowing from the heat exchanger may exceed the normal discharge temperature of water flowing from the hot water tank to the hot water supply system. To prevent any unexpected high temperature water from traveling through the hot water system a coaxial fitting is utilized. This fitting discharges the water from the heat exchanger a predetermined depth into the top of the tank such that the water from the heat exchanger mixes partially with the water in the tank before it may be discharged out the hot water outlet of the tank into the hot water system.